Code can never be reached because of a logical contradiction

Defect 100078 (STATIC_C)
Checker DEADCODE (subcategory none)
File: /src/jsonsl/jsonsl.c
Function jsonsl_util_unescape_ex
/src/jsonsl/jsonsl.c, line: 1364
Condition "--len == 0UL", taking false branch. Now the value of "len" is at least 1.
/src/jsonsl/jsonsl.c, line: 1382
Decrementing "len". The value of "len" is now at least 1.
/src/jsonsl/jsonsl.c, line: 1389
Condition "len < 6UL", taking false branch. Now the value of "len" is at least 6.
/src/jsonsl/jsonsl.c, line: 1427
Assigning: "len" -= "5UL".
/src/jsonsl/jsonsl.c, line: 1347
Decrementing "len". The value of "len" is now at least 0.
/src/jsonsl/jsonsl.c, line: 1347
Condition "len", taking true branch. Now the value of "len" is at least 1.
/src/jsonsl/jsonsl.c, line: 1354
Condition "len < 2UL", taking false branch. Now the value of "len" is at least 2.
/src/jsonsl/jsonsl.c, line: 1364
Decrementing "len". The value of "len" is now at least 1.
/src/jsonsl/jsonsl.c, line: 1364
At condition "-len == 0UL", the value of "-len" must be at least 1.
/src/jsonsl/jsonsl.c, line: 1364
The condition "--len == 0UL" cannot be true.
/src/jsonsl/jsonsl.c, line: 1365
Execution cannot reach this statement: "break;".